1. Field of Invention
The subject disclosure generally relates to pigment compositions and method of making pigment compositions.
This invention relates to a green pigment that lacks nickel in any form and a method of making it. The pigment is a solid solution of metal oxides including a [124] spinel which can contain certain combinations of lithium, sodium, cobalt, zinc, calcium, magnesium, copper, titanium, manganese, tin, and germanium, and a [134] spinel which can contain certain combinations of lithium, sodium, chromium, boron, iron, manganese aluminum, titanium, tin and germanium.
The green pigment produces colors similar to nickel containing green pigments and provides high hue angle and high TSR (total solar reflectance).
2. Description of Related Art
Pigments are widely used in various applications such as paints, inks, plastics, rubbers, ceramics, enamels, and glasses. There are various reasons for using inorganic pigments. Among these are the coloristic properties of the pigments, their visible as well as ultraviolet (UV) and infrared (IR) reflectance characteristics, their light fastness and their high temperature stability. The high temperature stability is necessary when the objects being colored are produced at elevated temperatures.
Pigments exhibit certain colors because they selectively reflect and absorb certain wavelengths of light. White light is an approximately equal mixture of the entire visible spectrum of light. When white light encounters a colored pigment, some wavelengths are absorbed as they interact with the electronic structure of the pigment. These interactions are determined by the chemistry and crystal structure of the pigment. The wavelengths not absorbed are reflected back to the observer, and this reflected visible light spectrum creates the appearance of a color. For example, ultramarine reflects blue light, typically between 400 and 500 nanometers in wavelength, and absorbs visible light of other wavelengths.
The appearance of pigments is also dependent upon the spectrum of the source light. Sunlight has a high color temperature and a fairly uniform spectrum, and is considered a standard for white light. Artificial light sources, including fluorescent light, tend to have great peaks in some regions of their spectrum, and deep valleys in other regions. Viewed under these conditions, pigments may exhibit different colors.